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| Research article summary (published 27 Jun 2002): |
Feedforward adaptations are used to compensate for a potential loss of balance.
Full Abstract
The central nervous system (CNS) must routinely compensate for unpredictable perturbations that occur during postural tasks. Such compensations could take the form of feedforward or feedback control. This study investigated whether the CNS, when faced with a potential postural perturbation, employs feedforward adjustments to reduce the near-term and overall likelihood of balance loss. Slips were induced, using bilateral low-friction platforms, during a sit-to-stand task in 60 safety-harnessed young adults. Subjects underwent a block of slipping trials, a block of nonslipping trials, then a mixed block of trials. After the first novel and unexpected slip, subjects were aware that a slip "may or may not occur." The state (horizontal position and velocity) of the body center of mass (COM) at seat-off and the direction of balance loss (forward, no loss, backward) were determined for each trial. Feedforward adjustments were identified as between-trial changes in COM state at seat-off. Effects of these adjustments on the likelihood of balance loss were quantified using logistic regression. Results indicated that the likelihood of balance loss in each direction (forward, backward) under each condition (slipping, nonslipping) was significantly related to the COM state at seat-off. When faced with the potential perturbation, the CNS made near-term feedforward adjustments to reduce the likelihood of balance loss under the conditions last experienced; exposure to slipping and nonslipping conditions resulted in adjustments that reduced the likelihood of backward and forward balance losses, respectively. Subjects adapted their performance over the longer-term in a manner that significantly decreased their overall likelihood of balance loss in either direction under either condition. The CNS thus adapted to acquire an "optimal" movement strategy that reduced the reliance on reactive responses to maintain balance in an uncertain environment.
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Author information
Author/s: Pavol, Michael J (MJ); Pai, Yi-Chung (YC);
Affiliation: Department of Physical Therapy (MC 898), University of Illinois at Chicago, 1919 West Taylor St., Fourth Floor, Chicago, IL 60612, USA.
Grants: R01-AG16727-01 (Agency:United States NIA)
Journal and publication information
Publication Type: Journal Article; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, P.H.S.
Journal: Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale (Exp Brain Res), published in Germany. (Language: eng)
Reference: 2002-Aug; vol 145 (issue 4) : pp 528-38
Dates: Created 2002/08/12; Completed 2002/11/06; Revised 2008/02/15;
PMID: 12172665, status: MEDLINE (last retrieval date: 11/6/2008)
Sourced from the National Library of Medicine. Abstract text and other information may be subject to copyright.
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